Synthesis of a Novel Core–Shell Nanocomposite Ag@SiO₂@Lu₂O₃:Gd/Yb/Er for Large Enhancing Upconversion Luminescence and Bioimaging

Upconversion nanocrystals have many advantages over other fluorescent materials. However, their upconversion luminescence intensities are not desirable, limiting their applications for highly sensitive detection. Therefore, it is really important to enhance upconversion luminescent intensities of upconversion nanocrystals. In the present study, a novel Ag core and upconversion nanocrystal shell based nanocomposite Ag@SiO2@Lu2O3:Gd/Yb/Er for metal-enhanced upconversion luminescence was fabricated successfully, and its morphology, crystalline phase, composition, optical property, and cell imaging application were investigated. It was found that a maximum upconversion luminescence enhancement of 30-fold was obtained in comparison with the control without a silver core, and the nanocomposite exhibited bright upconversion luminescence when it was used for imaging with HeLa cells. This enhancement potentially increases the overall upconversion nanocrystal detectability, endowing the nanocomposite with a potential capability for highly sensitive biological, medical, and optical detection.